Light attenuator

ABSTRACT

Light attenuator which is positioned between a flash fusing assembly and an electrophotographic recording surface to prevent light which emanates from the fuser from reaching the recording surface.

[11] 3,819,259 51 June 25, 1974 3,475,589 10/1969 Bartusek.........'................ 3628,440 12/1971 Czarnir0w.....

x N m e r n e D. x m R. 0A mm mm Ed TA T r m Hn w um Mfl UN [73] Assignee: Xerox Corporation, Stamford,

Conn.

Primary Examiner-John M. Horan [22] Filed: May 5, 1972 App]. No.: 250,636

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Michaels..........................

355/3 8 Claims, 7 Drawing Figures PATENTED Jllll 2 5 I974 SHEEI 1 (IF 3 1 LIGHT ATTENUATOR BACKGROUND OF THE INVENTION This invention relates to an apparatus for attenuating light. This invention further relates to the fusing station of an electrostatographic recording apparatus.

Electrostatography-is exemplified by the basic electrophotographic process taught by C. F. Carlson in US. Pat. No. 2,297,691, which involves placing a uniform electrostatic charge on a photoconductive insulating layer, exposing the layer to a light and a shadow image to dissipate the charge on the areas of the layer exposed to the light and developing the resulting latent electrostatic image by depositing on the image a finely divided electroscopic material referred to in the art as toner. The toner is normally attracted to those areas of the layer which retain a charge, thereby forming a toner image corresponding .to the latent electrostatic image, which may then be transferred to ,a support surface, suchas paper.

In general, the powder image is affixed to a transfer sheet by a heat fusing technique and among such techniques there may be mentioned oven fusing, hot air fusing, radiant fusing, flash fusing and the like. Flash fusing is a highly desireable fusing technique in that such a technique is efficient for both normal and high speed copying. Flash fusing is generally effected by the use of a gas lamp, such as a Xenon lamp, from which radiant energy is directed onto the surface of a recording sheet, containing a powder image, conveyed past the lamp. The radiant energy is reflected by those areas of the recording sheet which do not bear toner, while the toner on the other areas of the recording sheet absorb the radiant energy in the form of heat which is sufficient to effect the desired fusing.

In using flash fusing apparatus in an electrophotographic machine, any light which is transmitted from.

the fusing assembly to the electrophotographic recording surface could interfere with the electrophotographic process. Accordingly, it is advantageoustoprovide a fusing apparatus in which little or. no light is transmitted from the fuser to the electrophotographic.

surface.

SUMMARY OF THE INVENTION An object of the present invention is to provide an improved fusing apparatus.

Another object of the present invention is to provide an improved flash fusing apparatus.

A further object of the present invention is to provide a flash fusing apparatus for an electrophotographic reproducing apparatus in which light from the fuser is prevented from reaching the electrophotographic recording surface.

Still another object of the present invention is to provide an apparatus for passing material from or to a light sensitive station from or to a light producing station.

These and other objects. of the present invention should be more apparent from readingthe following description of the invention.

The objects of the present invention are accomplished in one aspect by providing an apparatus, including a housing through which a material is to be passed and a light blocking means, within thehousing, to prevent light which'enters the housing through either the inlet --or outlet thereof from being passed through the housing'to the other of the inlet or outlet.

More particularly, the light blocking means within the housing may includea housing'design such that the material passing through the housing changes directions, in the housing, to prevent a direct path of light from passing between the inlet and outlet thereof. The lighting blocking meansmay also include light interfering surfaces positioned in the housing between the inlet and outlet thereof in a manner such that both direct light and any reflected light, within the housing, does not pass between the inlet and outlet.

The light attenuating apparatus is particularly suited for an electrophotographic machine in which a transfer or recording member having av toner image thereon is to be passed from an'electrophotographic surface to a fusing apparatus which utilizes a light source as a source of fusing heat. The light attenuating apparatus is positioned between the electrophotographic surface and the fusing apparatusand the transfer member, having a toner image thereon, is passed from the electro-' photographic surface-to the fusing apparatus through the light attenuating apparatus in order to prevent light frombeing transmitted from the fuser to the electrophotographic surface.

Although thelight attenuating apparatus of the present invention'is particularly suited'for use in an electrophotographic machine, as described, the apparatus is also suitable for use in any. apparatus in which a material is to be passed from a light sensitive environment to a light emitting or from alight emitting environment to a light sensitive environment.

The present invention will be further described with respectto a preferred embodiment thereof, but it is to be understood that the scope of the invention is not to be limited thereby.

THE DRAWINGS FIG. 1 is a simplified schematic representation of electrophotographic apparatus including the fusing apparatus of the present invention;

FIG. 2 is a side. elevation of the fusing apparatus of the present invention;

FIG. 3'is a cross-sectional view taken along the line 33 in FIG. 3.

FIG. 4 is a front elevation of the support for'the fusinglamp;

FIG. 5 isanelevational view of the electrical connection for the lamp,

FIG. 6 is a side elevation of the light attenuator and FIG. 7 is a sectional view taken along 7-7 of FIG. 6.

Referring now to the drawings, there is shown schematieally in FIG. 1 an embodiment of the-subject invention in a suitable environment such as an electro photographic reproducing m'achine adapted for continuous and automatic operation. The machine includes an electrophotographic plate or surface 10 formed in the shape of'a drum. The plate'has a photoconductive or light responsive layer'on a conductive backing, journaled in a frame to rotate in the direction indicated by the arrow. The rotation will cause theplate to sequentially pass a series of electrophotographic processing stations. Forthepurpose of the present disclosure, the several electrophotographic processing stations in the 3 path of movement of the plate surface may be described functionally as follows:

A charging station A at which a uniform electrostatic charge is deposited on the photoconductive plate;

An exposure station B at which a light or radiation pattern of the copy to be reproduced is projected onto the plate surface to dissipate the charge in the exposed areas thereof to thereby form a latent electrostatic image of the copy to be reproduced;

A developing station C at which electrostatographic developing material, including toner particles having an electrostatic charge opposite that of the latent electrostatic image is cascaded over the plate surface whereby the toner particles adhere to the latent electrostatic image to form a visible toner image in a configuration of the copy being reproduced;

A transfer station D at which the toner image is electrostatically transferred from the plate surface to a transfer material or a support surface and A drum-cleaning station E at which the plate surface is brushed to remove residual toner particles remaining thereon after image transfer and exposed to a relatively bright light source to effect substantially complete discharge of any residual electrostatic charge remaining thereon.

It is felt that the preceding description of the electrophotographic process is sufficient for an understanding of the instant invention. Further details of this type of electrophotographic apparatus may be had by reference to US. Pat. No. 3,301,126 issued to R. F. Osborne et al.

in addition to the apparatus disclosed in aforementioned Osborne et a1. patent, the electrophotographic machine is also provided with fixing apparatus to permanently bond the toner image to the backing sheet and which forms the basis of the instant invention.

The sheet material, preferably paper, which is to form the final support for the permanent toner image, as shown, is a web of material 12 wound about a support roll 14 at a supply station. The web is directed along a feed path to pass the transfer station D and guided by an idler roller 22 to the fixing apparatus which includes a light attenuator 200 and a fuser assembly 100 with the web being passed through the light attenuator to the fuser assembly 100. The web having the fused image thereon is guided from the fuser assembly by a roller for ultimate withdrawal from the ma-. chine. The web may be subsequently cut into sheets as known in the art.

Referring to FIGS. 6 and 7, the light attenuator assembly 200 is comprised of a housing 201 having light absorbing interior surfaces formed of an upper section 202 and a lower section 203 which are fastened to each other by a suitable fastening means, such as screws 204, secured to mating longitudinal flanges 205 and 206 which extend along the length of the front and rear of the upper section 202 and lower section 203, respectively.

The bottom section defines an interior platform or floor 207 for supporting a web of recording material being passed through the housing 201. The portion 208 of platform 207 adjacent the drum extends angularly upwardly with respect to horizontal, and the portion 209 of platform 207 is positioned angularly downwardly with respect to the horizontal, whereby the direction of travel of the paper web is changed within the housing 201.

The upper section 202 defines a roof or top wall 211 for the housing 201 which is spaced from the lower platform 207. The roof 211 and platform 207, at the end adjacent the drum 10, define therebetween a narrow transverse inlet slit 212 for the recording web, and at the end adjacent the fuser 100, define therebetween anarrow transverse outlet slit 213 for withdrawing the recording web from the housing 201.

The platform 207 includes a guide means for guiding a recording member having a powder image thereon through the housing 201 in the form of two longitudinally spaced transverse rollers 214 and 215 journalled in transverse longitudinally spaced wells 216 and 217, respectively. The periphery of the rollers 214 and 215 extend above the platform 207 and are positioned with respect to each other and the inlet and outlet slits 212 and 213, respectively, in a manner such that the recording member changes direction in passing through the housing 201 to thereby prevent a direct light passage between the inlet and outlet. The upper section 202 is shaped in a manner such that the upper section is closely spaced to the lower platform 207 at the longitudinal ends of the housing and more widely spaced from the platform 207 at the intermediate portions thereof. The upper section is provided with a first light blocking surface in the form of an inwardly extending baffle defined by a transverse interior shoulder 218 between the wall 216 and inlet aperture 212, and a second light blocking surface in the form of a second light blocking baffle defined by an inwardly extending transverse generally U-shaped lip portion 219 at the end of the upper section 202 which defines the inlet slit 212 with the lower platform 207. The secondary light blocking surface defined by the lip 219 is positioned in a horizontal plane which is below the horizontal plane of the primary light blocking surface 218, whereby the secondary light blocking surface is in a position to block any light which may pass between the platform 207 and the primary light blocking surface 218.

The transfer sheet having the toner image thereon, which has passed through the light attenuator 200, is subsequently fused in the fuser assembly 100.

Referring to FIGS. 2 and 3, the fuser assembly includes a fuser housing 101 comprised of an upper section 102, defining a top wall 103, side walls 104 and 105, front wall 106 and a rear wall 107, and a lower section 108, defining a bottom wall 109. The bottom of the front and rear walls 106 and 107 of the upper section 102 are provided with outwardly extending longitudinal flanges 111 and the bottom section 108 is provided with longitudinal spacing bars 112 which extend parallel to the flanges 111 and are affixed thereto by suitable fastening means, such as screws 113. In this manner, the bottom wall 109 is spaced from each of the side walls 104 and to define therebetween transfer sheet inlet and outlet slits 114 and 115, respectively, for introducing and withdrawing a transfer sheet into and out of the fuser housing 101. The side wall 105 is further provided with a resilient seal means 116 which extends over the outlet slit 115' and is in contact with the bottom wall 109, with the transfer sheet being withdrawn from the housing 101 between the seal means 116 and the bottom wall 109. The seal means 116 is provided to inhibit leakage of light from the fuser.

The interior of the upper section of the fuser housing 101 is provided with an inner liner or shell 117 integrally connected to the upper section 102 and spaced therefrom to provide an insulating airgap l8 therebe tween. The inner surface 119 of the shell 117 is provided with a light reflecting'surface to maximize the transfer of heat to the transfer sheet being passed through the fuser housing 101. r

The fuser heating assembly 121 is comprised of a high intensity radiation source such as a pair of spaced flash lamps 122 each centrally positioned .in cylindrical glass cooling tubes 123 which are positioned transverse to the path of a transfer sheet through the fuser housing and which extend through aligned apertures 124' in the front and rear walls of the housing 101. An insulating tube 125, formed of a suitable insulating material, is telescopically received over the ends of each of the cooling tubes 123 and includes a collar receiving exterior radial flange 126 and an O-ring receiving interior circular shoulder 127. A fastening collar 128 is received over the flange 126 of insulating tube 125 and is removably fastened to the housing 101 by suitable fastening means, such as screws 129. An O-ring 131 is positioned on the shoulder 127 of insulating tube 125, and is seated into sealing contact with the shoulder 127, housing 101 and cooling tube 123 by tightening of the screws 129 on collar 128.

The flash lamps 122 are centrally supported in the cooling tubes 123 by retaining means in the form of resilient clips 141 which are removably received on the metal terminals 142 of theflash lampslZZ, which extend exteriorly of the cooling tubes 123. The clips 1.41 are comprised of a single resilient wire formed into a convoluted central portion 143 defining a cylindrical opening 144, axially spaced oppositely curved arcuate outer portions 145 and 146, which function as supporting legs, connected to the axially spaced ends of the central portion 143 by curved intennediate portions 147 and 148. The arcuate outer portions 147 and 148 are preferably each curved about equal radii having their respective centers along the central axis of the cylindrical opening 144 with each of the radii being such that the flash lamps 122 are positioned at about the center of the cooling tube 123.

The flash lamps 122 are mounted in the retaining clips 141 by spreading the top of the outer portions 145 and 146 to enlarge the opening 144 and placing the terminals 142 into the enlarged opening 144. Releasing of the outer portions 145 and 146 of the clip 141 results in the central portion 143 gripping the terminals 142 of the flash lamp 122.

Electrical connectors generally indicated as 151, are mounted on the tenninals 142 of the flash lamps 122 adjacent to the retaining clips 141. The electrical connector 151 are comprised of axially spaced parallel vertical arms 152 and 153 connected to each other by a horizontal connecting base 154 whereby the connectors 151 have a generally U-shape. The arms 152 and 153 are provided with axially spaced aligned apertures 155 and 156 which are slidingly fit over the lamp terminals 142. The upper ends of the arms 152 and 153 are provided with aligned screw holes adapted to receive a screw 157. The tightening of screw 157 causes the ends of arms 152 and 153 to move axially toward each other, thereby changing the effective diameter of the apertures 155 and 156, and providing a gripping connection between the connector 151 and the metal terminal 142. An electrical wire 158 which-enters the interior of the insulating tube 125 through an aperture 159 including a suitable seal, such as O-ring 161, is removably fastened to thebase 154 of connector 151 by a suitable fastening means, such as a screw 162. In this manner, the lamp terminals 142 are facilely connected to a suitable circuit and the electrical connection may be readily removed by the use of a screw driver which can easily be inserted into the insulating tubes 125.

The flash lamps 122 may be of a type known in the art, such as a quartz tube filled with a suitable gas, such as Xenon gas. The flash lamp 122 includes axially spaced electrodes 171 and a trigger coil 172 wrapped around the exterior of the gas filled tube. The trigger coil 172 is connected to a trigger circuit, of a type known in the art, which when activated provides a suitable high voltage pulse to the trigger coil 172. The operation of the flash lamp is well-known in the art and no detailed explanation thereof is deemed necessary for a full understanding of the present invention. Further details with respect to flash lamps may be obtained by reference to.U.S. Pat. No. 3,465,203; US. Pat. No. 3,445,626; and US. Pat. No. 3,529,129.

The flash lamps 122 are cooled by a coolant, preferably air obtained from the atmosphere, circulated through a cooling circuit which includes cooling tubes 123 and a pair of parallel transverse tubular return ducts 181 affixed to the outer portion of the lower section 108. The insulating tubes positioned on the rear wall 107 of housing 101 are connected through suitable duct work in fluid flow communication with a source of cooling air under pressure, such as a centrifugal blower which obtains cooling air from the atmosphere, and the insulating tubes 125 positioned on the front wall 106 of housing 101 are in fluid flow communication with the. return ducts 181 through removable right angle connectors 182 .and 183. The return ducts 181 are in fluid flow communication with suitable ducts for withdrawing the cooling air from the machine. In this manner, cooling air obtained from the atmosphere may be circulated around the flash lamps 122 and subsequently returned to the atmosphere.

In accordance with a particularly preferred embodiment of the fuser 100, each of the cooling tubes 123 at the portion thereof within the housing 101 adjacent to the rear wall 107 is provided with a small aperture 191 whereby air under pressure is introduced into the interior of housing 101. The small quantity of air introduced into the housing 101 circulates through the housing and is released therefrom through the recording sheet inlet and outlet slits 1 14 and 115. In this manner, the interior of the housing 101 is maintained under positive pressure and such positive pressure functions to maintain the interior of the housing essentially free of any machine or atmospheric dirt which could normally enter the housing 101.

In operation, the web having the transferred toner image thereon enters housing 201 through inlet slit 212 and is guided therethrough by the rollers 214 and 215 through outlet slit 213 and into the fuser 100. The web moves through the housing 201 in a generally horizontal direction with the first portion of the travel being slightly angularly upwardly with respect to horizontal and the second portion of travel being slightly angularly downwardly with respect to horizontal in order to effect the change in direction within the housing 201 to thereby aid in preventing light from being passed between the inlet and outlet of the housing.

The design and construction of thelight attenuator apparatus 200 is such that light does not pass between the inlet and outlet thereof. Direct light entering the outlet slit 213 which passes directly through the housing is intercepted primarily by the first light blocking baffle 218 and secondarily by the second light blocking bafi'le 219. Angllar light entering the housing through outlet slit 213 which is reflected from the interior surfaces of the housing is also intercepted primarily by the first light blocking baffle 218, and secondarily by the second light blocking baffle 219. The light absorbing interior surfaces of the housing 201 aid in minimizing the amount of light which is reflected in the housing.

Numerous modifications and variations of the hereinabove described embodiment are possible within the spirit and scope of the invention. Thus, for example, although the embodiment has been particularly described with respect to an electrophotographic reproducing machine, the light attenuator could be used in other environments in which a material is to be passed between a light sensitive station and a light emitting station. Similarly, although the embodimenthas been described with reference to a paper web as a'transfer member, the present invention is also applicable to sheet transfer members.

It is also to be understood that although the invention has been particularly described with respect to an electrophotographic member in the shape of drum the electrophotographic member can have other shapes; e.g., an endless belt.

The above modifications and others should be-apparent to those skilled in the art from the teachings herein.

The present invention is particularly advantageous in that a transfer sheet having a toner image thereon is facilely transported to thefusing apparatus while preventing light from being transmitted from the fusing apparatus to the electrophotographic recording member. The use of a separate light attenuating assembly permits the fuser to be designed in the manner best suited for its operation and without the necessity of placing the fuser in a position remote from the electrophotographic recording surface.

The above advantages and other shouldbe apparent to those skilled in the art from the teachings herein.

Numerous modifications and variations of the present invention are possible in light of the above teachings and, therefore, within the scope of the appended claims the invention may be practised other than as particularly described.

What is claimed is:

l. A light attenuating apparatus for passing a recording sheet having a powder image thereon from an electrophotographic recording member to a fusing assembly to prevent light from the fusing assembly from reaching the electrophotographic member comprising:

ward angle with respect to horizontal and downward angle with respect to horizontal and light blocking means within the housing to block any light which enters the housing through said outlet of the housing to thereby prevent any light which enters the outlet from reaching the inlet of the housing.

2. The apparatus of claim 1 wherein the light blocking means comprises first and second substantially vertical extending light blocking baffles on the interior surface of said housing, said first light blocking baffle being positioned closer to said outlet and in a horizontal plane above said second light blocking baffle.

3. The apparatus of claim 2 wherein said guide means comprises a substantially horizontal platform by which the recording sheet is guided from the inlet to the outlet, said platform including a first portion which is inclined angularly upwardly with respect to horizontal and a second portion which is inclined angularly downwardly with respect to. horizontal.

4. In combination with an electrophotographic recording member and a fuser assembly having an inlet for receiving a recording sheet having a powder image thereon from the recording member, a light attenuating apparatus for blocking light from the fuser assembly from reaching the electrophotographic member comprising:

a housing including an inlet slit for the recording sheet and an outlet slit for the recording sheet, said housing being positioned between the recording member and fusing assembly with the inlet slit adjacent to the recording member for receiving a recording sheet having a powder image thereon from the recording member and with the outlet slit adjacent to the inlet of the fusing assembly for delivering the recording sheet with the powder image thereon directly into the fusing assembly; guide means within the housing for guiding the recording sheet through the housing between the inlet and outlet slits; and light blocking means within the housing to block any light from the fuser assembly which enters the outlet slit of the housing and to thereby prevent the light from reaching the electrophotographic recording member through the inlet slit.

5. The apparatus of claim 4 wherein the housing has light absorbing interior surfaces and the guide means guides the recording sheet in a substantially horizontal direction, said guide means guiding the recording sheet in said substantially horizontal direction in both an upward angle with respect to horizontal and a downward angle with respect to horizontal.

6. The apparatus of claim 5 wherein said guide rrieans comprises-a substantially horizontal platform by which the recording sheet is guided from the inlet to the outlet, said platform including a first portion which is inclined angularly upwardly with respect to horizontal and a second portion which is inclined angularly downwardly with respect to horizontal.

7. The apparatus of claim 6 wherein the light blocking means comprises first and second substantially vertical extending light blocking baffles on the interior surface of said housing, said first light blocking baffle being positioned closer to said outlet and in a horizontal plane above said second light blocking baffle.

8. The apparatus of claim 5 wherein said fuser assembly is a flash fuser. 

1. A light attenuating apparatus for passing a recording sheet having a powder image thereon from an electrophotographic recording member to a fusing assembly to prevent light from the fusing assembly from reaching the electrophotographic member comprising: a housing including an inlet slit at one end for receiving a recording sheet from an electrophotographic recording member and an outlet slit at another end for delivering a recording sheet, to a fusing assembly, said housing having light absorbing interior surfaces, a guide means within the housing for guiding the recording sheet from the inlet to the outlet in a substantially horizontal direction, said guide meAns guiding the recording sheet in said substantially horizontal direction in both an upward angle with respect to horizontal and downward angle with respect to horizontal and light blocking means within the housing to block any light which enters the housing through said outlet of the housing to thereby prevent any light which enters the outlet from reaching the inlet of the housing.
 2. The apparatus of claim 1 wherein the light blocking means comprises first and second substantially vertical extending light blocking baffles on the interior surface of said housing, said first light blocking baffle being positioned closer to said outlet and in a horizontal plane above said second light blocking baffle.
 3. The apparatus of claim 2 wherein said guide means comprises a substantially horizontal platform by which the recording sheet is guided from the inlet to the outlet, said platform including a first portion which is inclined angularly upwardly with respect to horizontal and a second portion which is inclined angularly downwardly with respect to horizontal.
 4. In combination with an electrophotographic recording member and a fuser assembly having an inlet for receiving a recording sheet having a powder image thereon from the recording member, a light attenuating apparatus for blocking light from the fuser assembly from reaching the electrophotographic member comprising: a housing including an inlet slit for the recording sheet and an outlet slit for the recording sheet, said housing being positioned between the recording member and fusing assembly with the inlet slit adjacent to the recording member for receiving a recording sheet having a powder image thereon from the recording member and with the outlet slit adjacent to the inlet of the fusing assembly for delivering the recording sheet with the powder image thereon directly into the fusing assembly; guide means within the housing for guiding the recording sheet through the housing between the inlet and outlet slits; and light blocking means within the housing to block any light from the fuser assembly which enters the outlet slit of the housing and to thereby prevent the light from reaching the electrophotographic recording member through the inlet slit.
 5. The apparatus of claim 4 wherein the housing has light absorbing interior surfaces and the guide means guides the recording sheet in a substantially horizontal direction, said guide means guiding the recording sheet in said substantially horizontal direction in both an upward angle with respect to horizontal and a downward angle with respect to horizontal.
 6. The apparatus of claim 5 wherein said guide means comprises a substantially horizontal platform by which the recording sheet is guided from the inlet to the outlet, said platform including a first portion which is inclined angularly upwardly with respect to horizontal and a second portion which is inclined angularly downwardly with respect to horizontal.
 7. The apparatus of claim 6 wherein the light blocking means comprises first and second substantially vertical extending light blocking baffles on the interior surface of said housing, said first light blocking baffle being positioned closer to said outlet and in a horizontal plane above said second light blocking baffle.
 8. The apparatus of claim 5 wherein said fuser assembly is a flash fuser. 